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Origin and construction of the bridge

The situation of a hunting lodge on the limestone monadrock raised above water in the middle of Portz pond (also known as Nový), built in the late Middle Ages, also raised a question of accessibility of the site across the broad expanse of water. It is hard to imagine the delivery of building materials for the construction could only be secured by boat. This may prompt a consideration that already during the summer house construction, perhaps some time during the 1620s, there existed access to the island by land, i.e. via a bridge. Historical sources do not specify the construction of a brick bridge on Portz Insel, so we may only wonder whether it was already in place during the summer residence construction, or it was preceded by some temporary wooden structure.

The bridge located at the narrowest point of the pond still reached a respectable length of 95 m, its width being 3.70 m. It consists of fifteen semicircular vaulted arches, divided by pilasters with double-sided pyramidal edges. The bridge deck was lined with a solid, approx. 75 cm high parapet wall. The outer fully bricked sections were ended with short open wings with decoratively shaped fenders at the ends. The tenth section of the bridge from the south had originally been a wooden lifting deck; it was still documented on the maps from as late as the 1830s, but shortly afterwards it was removed and the empty section was bricked up in a similar manner as the other parts of the bridge. After being vaulted, the part of the deck in the originally unfilled segment was also paved with limestone cubes. During the present restoration, accompanied by archeological survey, it was found that the stone pavement had an approx. 5–10 cm thick layer of fine limestone gravel on it. The engineering design of the bridge was very well thought out. The part of the columns below and slightly above the water surface was made of large blocks of hewed stone, the remainder was built of brick. The bridge arches themselves widen at two points towards the base and the bricks on the front face are hewed in the shape of a decorative arch keystone. Also the pyramidal shape of the edges was obtained through final hewing the brick masonry to shape. Uniquely preserved is the drainage solution for the bridge deck, using drainage openings lined with curved roof tiles, known as tegulas.

Historical plan of the bridge

Historical plan of the original bridge design still with the lifting deck Source: Moravian Provincial Archive, Brno, collection F18, the Main Filing Cabinets of the Dietrichsteins in Mikulov, Historical plan of the original bridge design still with the lifting deck, undated, map 107.

Cutout from the overall 3D model of the bridge

The picture shows a cutout of the overall 3D model of the bridge created by laser scanning within an archeological survey in 2019. The purpose of the scanning was to identify the scope of the preserved original elements of the bridge. A later alteration is visible on the first arch from the left, where the extended vault replaced the old wooden drawbridge. Source: Ing. Miloš Tejkal